Identification of a chemical marker of environmental exposure to formaldehyde

Formaldehyde (F) binds human serum albumin (HSA) covalently, giving rise to a molecular adduct F-HSA having the F as hapten. The humoral immune response to the adduct provides a biological marker of F exposure. In order to titrate serum anti-F-HSA antibodies, a new indirect competitive enzyme immunoassay (displacement assay) was developed. Two groups of about 90 heterogeneous healthy subjects were examined using two in vitro conjugated F-HSA adducts with different ratios between F and HSA (5:1 and 10:1). Contingency table analysis showed a greater sensitivity (97%) and specificity (92%) of the test with the 10:1 F-HSA adduct than with the 5:1. Data examination using multivariate analysis of variance revealed that in both groups the smoking variable significantly explains (P<0.01) the values of the F exposure marker. A significant association with immunological response was obtained only in male smokers, using 5:1 F-HSA adduct, while with 10:1 ratio, a good association in male and female smokers was found. Results confirm that the immunological assay developed (displacement assay) could be a useful method for evaluating F exposure, especially for public health monitoring on a large scale.